1. Field of the Invention
The present invention relates to a rotary connector for electrically connecting between a pair of housings, which are connected so as to be rotatable relative to each other, through a flexible cable.
2. Description of the Related Art
A rotary connector is briefly comprised of a pair of housings connected so as to be rotatable relative to each other, and a flexible cable wound around a storage section defined between the housings. Both ends of the flexible cable are electrically led out of each of the housings while being fixed thereto. One of the housings is used as a movable member and the other one is used as a stationary member. When the movable housing is rotated in both normal and reverse directions, the flexible cable is wound up or rewound in the storage section in accordance with the direction of rotation.
FIG. 5 is a vertical sectional view showing a conventional rotary connector. As shown in FIG. 5, a fixed housing 1 has a bottom plate 2 and a cylindrical member 3 which are integrated with each other, and a center hole 4 is formed in the center of the bottom plate 2. The cylindrical member 3 is provided with an outer cylinder 5 rising on the outer periphery of the bottom plate 2 and a first top plate 6 extending inwardly from the upper end of the outer cylinder 5. On the other hand, a movable housing 7 has an inner cylinder 8 and a second top plate 9 outwardly extending from the upper end thereof, and a stepped portion formed on the second top plate 9 overlaps the lower surface of the first top plate 6. A ring-shaped storage section 10 is defined between the housings 1 and 7, and a flexible cable 11 is, for example, spirally wound into the storage section 10. One end of the flexible cable 11 is led out of the housing 1 while being fixed to the outer cylinder 5, and the other end is led out of the movable housing 7 while being fixed to the inner cylinder 8.
The rotary connector thus briefly constructed is incorporated in a steering system of an automobile, and used as an electrical connecting means such as an air bag circuit or a horn circuit in such a manner that the fixed housing 1 is mounted to a combination switch which is a stator member of the steering system, and the movable housing is mounted to a handle which is a rotor member of the steering system. In the use of the rotary connector, when the handle is turned clockwise or counterclockwise, the turning force is transmitted to the movable housing 7 to rotate the movable housing 7 clockwise or counterclockwise. As a result, the flexible cable 11 is wound and tightened around the inner cylinder 8, or rewound around the outer cylinder 5, so that electrical connection between the housings 1 and 7 is maintained through the flexible cable 11 in both conditions.
In the conventional rotary connector, the second top plate 9 of the movable housing 7 overlaps the lower surface of the first top plate 6 inside the outer cylinder 5 of the fixed housing 1. Thus, even if external members such as column covers, etc. are arranged in the vicinity of the outer cylinder upon incorporation in the steering system, the rotation of the movable housing 7 can be prevented from being interrupted by the external members. However, since a spacing S formed in the overlapping portion of the first and second top plates 6 and 9 is located on the upper surface of the rotary connector, foreign substances such as dust or an erroneously spilled beverage tend to enter the storage section 10 from the spacing S, whereby the connection reliability of the flexible cable 11 deteriorates.
In addition, when the foreign substance is a liquid such as a beverage, the liquid easily enters the storage section 10 from the spacing S by capillary action.